Continuous process for the preparation of dithiophosphate acid esters



Dec. 2, 1958 F. c. GOLDSMITH 2,862,947

CONTINUOUS PROCESS FOR THE PREPARATION OF DITHIOPHOSPHATE ACID ESTERSFiled Dec. 20. 1951 :s Sheets-Sheet 1 INVENTOR. FEED CORW/IV GOLD/Y I771BY j g 2 7 A! ORA/E76.

Dec. 2, 1958 F. c. GOLDSMITH CONTINUOUS PROCESS FOR THE PREPARATION OF-DITHIOPHOSPHATE ACID ESTERS Filed D60. 20 1951 5 SheetsSheet 2 IINVENTOR. FRED conww (:04 05M m1 {Mai ATTOIZNEYS 1958 c. GOLDSMITH2,862,947

. F- CONTINUOUS PROCESS FOR THE PREPARATION OF DITHIOPHOSPHATE ACIDESTERS Filed Dec. 20, 1951 3 Sheets-Sheet 3 FRED amen 0v cmwM/T iATTOZ/VEXS CONTINUOUS PROCES FGR THE PREPARATEQN OF DITHIOPHQSPHATE ACIDESTERS Fred Corwin Goldsmith, Painesville, Uhio, assignor to TheLuhrizol Corporation, Wicklifite, Ohio, .21 corpora- This inventionrelates as indicatedto a process and apparatus for reacting a pluralityof reagents, at least one of which is a fluid, and more specifically aliquid, and at least one of which is a solid, and more particularlywherein the specific gravities of said fluid and solid reagents aresubstantially difierent.

By the present invention, the reaction is carried out with the reagentsin the form of a slurry which is continuously circulated. By continuousor intermittent replenishment of the reagents taken up by the reactionand preferably also by the continuous or intermittent withdrawal of theproducts formed, the process may be made fully continuous.

The process and apparatus of this invention are adapted for use withboth endothermic and exothermic reactions since it is relatively easy toefiect the necessary temperature control as by heating or cooling of thereaction mass as it is circulated.

As indicated, the invention is particularly adapted for use in efiectivereactions wherein the reagents have measurable differences in specificgravity and especially in connection with reactions which permit thepresence in the reaction mass of substantial excesses of one of thereagents since by maintaining those conditions it has been foundpossible to control the rate of replenishment of the reagents by simplemeans such as density responsive equipment.

More particularly, the invention is applicable to reactions such asthose wherein a solid such as phosphorus sulphide is reacted with anorganic hydroxy compound such as an alcohol in the production ofdithiophosphoric acid esters.

It is therefore a principal" object of my invention to provide a processand apparatus by which reactions of the character defined may be carriedout expeditiously, at low cost and by the use of simple equipment whichmay be readily controlled.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description and the annexeddrawings setting forth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but a few of the variousways in which the principle f the invention may be employed.

In said annexed drawings:

Fig. 1 is a generally diagrammatic showing of the preferred form ofapplicants invention;

Fig. 2 is a diagrammatic showing of one type densorneter, or densitycontrol device, which may be used in applicants apparatus; a

Fig. 3 is a detailed showing of the glass tube 34 in Fig. 2; and

Fig. 4 is the electrical, circuit of the control device which may beused in applicantsapparatus.

Broadly stated, this invention comprises the provision of apparatuscapable of performing the process of this invention which process may bebroadly defined as the process of reacting solid and liquid reagents toform a liquid product, the steps of continuously circulating in a closedsystem a slurry of at least one solid reagent, the major portion of theliquid phase of said slurry being inert to the desired reaction,introducing into said closed system at least one reagent at rates so asto maintain said solid reagent at every point in said system in amountsgreatly in excess of the minimum amounts required for complete reactionwith the amount of liquid reagent present at that point, maintaining thetemperature of the continuously circulating stream of slurry for asubstantial portion of its circulating cycle at a temperature favorableto the desired reaction, and drawing off from the system liquid productat about its rate of formation.

Referring now more particularly to the preferred form of my invention inFig. 1 one hundred gallons of slurry 1, comprising solid reagentssuspended in a mixture of a small proportion of liquid reagent and arelatively large proportion of the diluent, which can be an inertmaterial or preferably the liquid product of the reaction of the solidreagent with the liquid reagent, is maintained at a uniiorm temperaturein reactor 2. The solid reagents form the solid phase and the diluentthe liquid phase of the slurry. The slurry is agitated in the kettle bystirrer 3 and vanes 7 attached to the Wall of the kettle. Powdered solidreagent is loaded into feed hopper 4 located above reactor 2. The solidreagent is continuously fed into the reactor 2 from hopper i by means ofa revolving vertical screw 5 extending into the top of the reactor. Thescrew 5 fits the barrel 6 of the hopper 4 closely and provides gas-tightseal between hopper land kettle 2. Liquid reagent is continuously fedinto the slurry by line 8 connected to line 9, or if desired by a lineconnected into the top of reactor 2. The liquid reagent and solidreagent reactin reactor 2, forming a liquid product and liberating agas. A vertical weir lltb is provided in reactor 2. A bafile ll isspaced from Weir it and provides a quiescent zone around the weir 10. Aportion of the slurry in the reactor overflows continuously weir 10 andflows down line 20 into solids separator 12 located below the reactor.The decanted liquid phase of the slurry, essentially free of solidreagent, overflows the side of separator 12, into the receiver 3'13. Thesolid reagent enriched separator slurry stream is fed to a pump 14 andreturned to the reactor 2 by line 9. The liquid phase of the slurry ispumped from the receiver 13 by pump 22 to suitable storage tanks, notshown. If the diluent is a material other than the reaction product ofthe solid and liquid reagents, further steps will have to be taken toseparate the diluent and product. For this purpose a flash evaporator 60can be employed to evaporate the diluent and conduct the diluent vaporby line 611 to cooler 18 where the diluent is condensed and returned tothe slurry by line 19. Thus, it is desirable for most purposes to usewhere possible the reaction product as the diluent.

The by-product gas atmospheres in the reactor 2, separator l2, andreceiver 13 are collected in lines 14A, 15, 16, respectively, connectedto common line 17. The byproduct gas liberated is normally saturatedwith evaporated liquid reagent. The gas stream is passed by common line17 to gas cooler 13, and the liquid reagent condensate is run back intoreactor 2 by line 19. The cooled gas then passes to an absorber by line21, not shown, or is disposed of in some other way.

The density of the slurry l. in reactor 2 is determined continuously bytwo nitrogen probes in the reactor 2, referred to generally in Figure lby reference 23. Referring now to the densometer, in Figure 2, an upperprobe 24 vents to the gas space in; the reactor 2 and measures the gaspressure above the slurry i. The lower probe Patented Dec. 2, 1958 .3 25extends near the bottom of the reactor 2 and measures the Weight of theslurry above the lower probe to the height of weir in Figure l, the weir10 being a means for providing a constant height of slurry. Thedifference between the two pressures provides a means for measuring theaverage slurry density. The specific gravity of the solid reagent issubstantially different from the liquid phase of the slurry so that, asthe concentration of solid reagent in the slurry increases, the densityincreases; and as the concentration of solid reagent'in the slurrydecreases, the density decreases. Thus, the measured density provides ameans for controlling the feed ratios of the reagents. Theliquid reag ntfeed may be kept constant and the solid reagent feed varied, or thesolid reagent feed may be held constant and the liquid reagent feedvaried. The first method is used in this unit, but the latter method maybe used equally well. The upper nitrogen probe 24 and the lower nitrogenprobe 25 are supplied with nitrogen from a'supply line 26 at a pressureof about pounds per square inch gauge. The nitrogen gas flows through asurge chamber 2'7where any foreign particles drop out. From the surgechamber the nitrogen flows through flow regulators 28 which regulate thefiow to the system probe tubes at a constant rate of one cubic foot perhour. On the lower probe side, the flow goes to the lower probeequilibrium chamber 29, the densometer manometer 30, and to lower probein the reactor 2. On the upper probe side, the flow goes to the upperprobe equilibrium chamber 31, and to an oil equalizing tank 32 throughwhich the pressure drops; this drop being roughly equivalent to thepressure drop of the lower probe in reactor 2. The nitrogen outlet fromthe oil equalizing tank goes to the top of densometer manometer 30, tothe system pressure manometer 33, and to upper probe 24-. The systempressure manometer 33 indicates the gas pressure within the system. Thedensometer manometer indicates the difference between the pressure onthe lower probe 25 and the gas pressure in the system. This reading is adirect reading of the density of the material in the reactor 2 at theoperating conditions, since the level of the material in the reactor 2is kept constant by overflow weir 16. The function of the oil equalizingtank 32 is to decrease this differential reading under normal operatingconditions to approximately zero between the upper and lower probeequilibrium chambers 29, 31. A differential manometer is {used tomagnify the density changes inpthe reactor 2.

density, or feeding solid reagent with alcohol feed detube 34 isprovided with a trap 37 to remove foreign particles from the keroseneand a trap 38 to remove particles from the dichromate solution. Threewires A, B,

lead from the glass contact tube 34 to the electrical control device.The A and B contacts are limit controls connected to two platinumcontact electrodes spaced two inches apart in glass tube 34. The Ccontact is a common ground. The A contact, or upper contact, shuts offthe solid reagent feed when the circuit of A to C through I contact andbreaks the holding circuit in the electrical control device, and alsocompletes the circuit to the feed screw to start feeding of solidreagent again into reactor 2.

On Figure 4, lines X, Y are an A. C. supply. Switch 43 is a double poledouble throw type to switch the solid 1 reagent feed from automatic tomanual control, indicated This is done by using a small diameter glasstube 34 conv 'nected between the bottom of the upper probe equilibriumchamber 31 and the bottom of lower probe equilibrium chamber 29.Manometer fluids of kerosene and a" 4% dichromate solution are used.Since the glass tube diameter is smaller than the diameter ofequilibrium chambers 29, 31, the movement of liquid in the chamber tocause a 2 inch or 3 inch movement in the glass tube is negligible. Thedichromate-kerosene interface is adjusted to the midpoint of the glasstube 34 and gives a magnification of:

1 1 d (dieh.) d. (kero.) 1.00.8

where d.(dich.) and d.(kero.) represent the density of the dichromatesolution and kerosene, respectively. Or, if the reading on thedensometer manometer 30 varies one inch, the reading on the glasscontact tube will vary five inches. By inserting two platinum contactelectrodes, ,two inches apart in the glass tube, the densometermanometer 30 can be controlled to 0.4 inch water column readingdifference.

The densometer equilibrium valve 35 regulates the density range. Thedensity of the slurry is allowed to build up with the valve open; uponclosing the valve 35, the glass contact tube 34 takes over and controlsthe density. If a higher or lower value of density is desired, :thevalve 35 is opened and the density adjusted by feedalcohol with thesolid reagent feed off to lower by letters N and M. When the switch isin the manual position M, the A. C. supply X, Y is connected toterminals 46, 47. In the automatic position N, the A. C. supply X, Y isconnected to terminals 44, 45. A jumper connects terminals 45, 47. Thefollowing discussion will assume switch 43 is in automatic position, N.Current is supplied to the primary coil L of relay 48. Coil L is asecondary coil energized by L when its circuit is closed. An A-shapediron core is provided for L L Two switches S S are mounted on movablearm 49. Coil L is always energized and tends to move arm 49 to closeswitch S and terminals 50, 51. Coil L when energized, bucks theelectromagnetic force of coil L to move arm 49 to close switch S andterminals 52, 53, and also to open S and terminals 50, 51. To illustratea typical cycle of operation, as the density increases and thedichromate solution rises in glass tube 34, it first contacts B. Nothinghappens because the holding switch S is open at 52, 53 and L normallyholds S closed. When the dichromate solution rises to A, the circuit ofsecondary coil L is closed through the liquid A to C, which causes abucking action to take place in the core of secondary coil L closingswitch S and opening switch S The armature 49 is held in this positionby the holding circuit B to C through S keeping L energized until thedichromate solution drops below B. As the density decreases in thereactor and the dichromate solution drops below contact B, the circuit Bto C is broken at which time S is closed by L to operate motor M andfeed the solid reagent to the reactor and again increase the densityuntil the dichromate solution in glass tube 34 again rises to contact Aand S is opened. It will be noted that the switch S operates motor M.which drives the feed screw 5 in hopper 4 feeding solid reagent intoreactor 2. The hopper 4 is provided with a vibrator 54 as to aid theflow of solid reagent. The direct current necessary for operation of thevibrator is supplied by rectifier tube 55 which must be energized beforeuse. This is accomplished by means of a time delay clock relay T whichcloses switch S and the vibrator circuit only after the rectifier hasreached operating conditions. A rheostat R is provided to controloperation of vibrator 54.

It is to be understood that although an electrical control device hasbeen described above which controls the rate of solid reagent feed whilea constant rate of feed of liquid reagent is maintained, other systemsmay be employed equally well. Pneumatic and hydraulic control systemsare generally equivalent to electrical systems and may be employed, forinstance, to Vary the liquid reagent feed while the solid reagent iskept constant.

The solid reagent should have a specific gravity that is substantiallydifferent from the liquid phase of the slurry. In the process andapparatus of this invention it is desirable to employ a solid reagentwith ya specific gravity substantially greater than the specific gravityof the liquid phase of the slurry.

The solid reagent employed should be in a finely divided state, and itis preferably to use a solid reagent which will pass through No. U. S.Standard Screen.

In the preparation of organic dithiophosphate materials the solidreagent can be compounds of phosphorus and sulphur, for example:

For many purposes, phosphorus pentasulfide will be found especiallyuseful as a solid reagent.

The liquid reagent can be an organic hydroxy-containing body, forexample:

MONOHYDRIC AND DIHYDRIC ALCOHOLS I. Aliphatic mono-hydric alcoholsMethyl Hexyl Ethyl Heptyl Propyl: Octyl:

Iso-propyl n-Octyl Butyl: sec.-Octyl, e g. capryl n-Butyl 2-ethy1 hexylsec.-Butyl Decyl tert.-Butyl Dodecyl: iso-Butyl Lauryl Amyl Lorol n-AmylHexadecyl: sec.-Amyl Cetyl tert.-Butyl carbinol Heptadecyl iso-AmylHeptadecenyl Octadecyl ll. Cycloaliphatic mono-hydric alcohols A.Mono-hydric cycloaliphatic alcohols having the OH- radical-attached to acycloaliphatic nucleus:

Cyclopropyl Cyclohexyl Methyl cyclohexyl Propyl cyclohexyl Iso-propylcyclohexyl Butyl cyclohexyl n-Butyl cyclohexyl tert.-Butyl cyclohexylAmyl cyclohexyl Cyclohexyl cyclohexyl Mixtures of cyclohexanol and itshomologues Mixtures of homologues of cyclohexanol CycloheptanolHydrogenated naphthols:

Decahydro ,8 naphthol Decahydro on naphthol Tetrahydro ,8 naphtholTetrahydro a naphthol Furfuryl alcohol Tetrahydrofurfuryl alcoholHydrogenated phenols:

Tetrahydro phenol Cyclohexanol Bornyl alcohols:

Bcrneol IZI. Aliphatic di-hydric alcohols Ethylene glycol Diethyleneglycol Propandiols, e. g.

Propandiol-1,2 Propandiol-LB Butandiols, e. g.

Butandiol-l,2 Butandiol-2,3 Butandiol1,3 Tetramethylene glycolHexandiols, e. g.

Hexamethylene glycol Octandiols, e. g.

Octamethylene glycol 2-ethyl hexandiol-1,3

' Decandiols, e. g.

Decamethylene glycol IV. Cycloaliphatic di-hydric alcoholsHexahydro-hydroquinone Hexahydrodesorcinol POLYHYDRIC ALCOHOLS GlycerolButanediol Pentanediol Pentaerythritol Tetramethylol cyclohexanolXylylene glycol If the alcohol is a solid it can be dissolved in asolvent and in that manner be employed as a liquid reagent in theprocess.

The following table summarizes typical operating conditions in theprocess and apparatus described above for the preparation of organicdithiophosphate materials by u the reaction of P 8 and alcohols.

TYPE OF ALCOHOL Methyl-iso- Iso-prop 1 Item Condition butyl alcoholBlend 1 carbinol A Alfiohol feed rate, lbs./ 472 277 700 r. B P285 feedrate lbs./hr 244 244 293 o Acid rate, lbsf/hr 619 483 948 D H2S rate,lbs/hr 37 38 45 E Operating temp, F 210 210 F Operatmg density".-. 0.955-0. 972 1 (MO-1.058 0 918-0. 936 G Percent P28 in slurry. 6-8

1 Blend37.5'7 n-octyl alcohol 37.5 meth l-iso-but lcarblnol 25 n-hexylalcohoL y y To persons skilled in the art a description of the operationof the process and apparatus constituting the present invention will befound useful. In the preparation of organic dithiophosphate acid estersby the reaction of '7 P S and alcohols, the reaction can be illustratedby the following equation:

PQS+4ROH 2 +HgS RO/ SE The liquid organic dithiophosphate acid ester ispreferred as the diluent in this process. To operate the apparatus, thenitrogen probes 24, 25, are turned on and the densometer equilibriumvalve 35 is opened. When the densometer valve 35 is opened and shut-0Evalves for the glass contact tube are opened, the dichromate-keroseneinterface should ride between the platinum contacts A and B. If this isnot the case an adjustment should be made by adding or removing thedichromate solution. The alcohol is fed into reactor 2 heated toreaction temperature (see item B in the table above) after the alcoholoverflows weir 10, the alcohol is shut off. The P 5 feed is begun (seeitem B in table above). When the densometer manometer indicates 90% ofthe desired density (see item F above) the alcohol feed is begun atone-half the normal feed rate (see item A above). The densometer valve35 is closed at the desired density and switch 43 thrown to automaticposition to automatically regulate the P 5 feed rate. Over a four hourperiod the alcohol feed rate is gradually increased to normal. Theslurry, comprising essentially organic dithiophosphate acid ester and PS is continuously circulated from reactor 2, over weir 10, to separator12, and then back to reactor 2 by pump 14 and line 9. When the densityof the slurry increases in reactor 2 above a certain value,

the automatic control shuts the P S feed ofi until thedensity fallsbelow a particular point, at which time the P 8 feed is resumedautomatically. The P S is maintained at every point in the system inamounts greatly in excess of the minimum amounts required for completereaction with the alcohol present at that point. Thus, the alcohol whenintroduced into the slurry reacts almost immediately with the P 8 toinsure accurate control of the rates of feed by the densometer. Theorganic dithiophosphate acid ester is decanted essentially free of P 8from separator 12 to receiver 13. It has been found that it is equallysatisfactory to vary the alcohol fe'ed rate while maintaining constantthe P 8 feed rate.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In the method of reacting at least one phosphorus sulfide and analcoholic body to form a dithiophosphate acid ester the process whichcomprises agitating a slurry containing phosphorus sulfide anddithiophosphate acid ester, maintaining said slurry at a constant level,measuring the density of said slurry, introducing phosphorus sulfide andan alcoholic body in proportions as determined by said densitymeasurements so as to maintain the phosphorus sulfide in said slurry inamounts greatly in excess of the minimum amounts required for completereaction with the alcoholic body present in said slurry, drawing olfhydrogen sulfide gas and decanting the dithiophosphate acid esterproduct from the system.

2. In the process of reacting a phosphorus sulfide and an alcoholic bodyto form a dithiophosphate acid ester and hydrogen sulfide, the steps ofcontinuously circulating in a closed system a slurry of said phosphorussulfide, the major portion of the liquid phase of said slurry being thedithiophosphate acid ester, introducing into said closed system saidphosphorus sulfide and alcoholic body at rates so as to maintain saidphosphorus sulfide at every point in said system in amounts greatly inexcess of the minimum amounts required for a complete reaction with theamount of organic hydroxy compound present at that point, maintainingthe temperature of the continuously circulating stream of slurry for asubstantial portion of its circulating cycle at a temperature favorableto the desired reaction and drawing off from the system the liquiddithiophosphate acid ester at about its rate of formation.

3. The process of claim 2 characterized further in that the phosphorussulfide is phosphorus pentasulfide and the organic hydroxy compound isan aliphatic alcohol.

4. The process of claim 2 characterized further in that the phosphorussulfide is phosphorus pentasulfide and the organic hydroxy compound is alow molecular weight alcohol.

References Cited in the file of this patent UNITED STATES PATENTS1,210,180 Logan Dec. 26, 1916 1,530,833 Keeler Mar. 24, 1925 1,748,619Romieux et a1 Feb. 25, 1930 1,889,943 Barsky et a1. Dec. 6, 19321,947,852 Jewett Feb. 20, 1934 2,160,177 Shuman May 30, 1939 2,374,507Schulze Apr. 24, 1945

2. IN THE PROCESS OF REACTING A PHOSPHORUS SULFIDE AND AN ALCOHOLIC BODYTO FORM A DITHIOPHOSPHATE ACID ESTER AND HYDROGEN SULFIDE, THE STEPS OFCONTINUOUSLY CIRCULATING IN A CLOSED SYSTEM A SLURRY OF SAID PHOSPHORUSSULFIDE, THE MAJOR PORTION OF THE LIQUID PHASE OF SAID SLURRY BEING THEDITHIOPHOSPHATE ACID ESTER, INTRODUCING INTO SAID CLOSED SYSTEM SAIDPHOSPHORUS SULFIDE AND ALCHOLIC BODY AT RATES SO AS TO MAINTAIN SAIDPHOSPHORUS SULFIDE AT EVERY POINT IN SAID SYSTEM IN AMOUNTS GREATLY INEXCESS OF THE MINIMUM AMOUNTS REQUIRED FOR A COMPLETE REACTION WITH THEAMOUNT OF ORGANIC HYDROXY COMPOUND PRESENT AT THAT POINT, AMINTAININGTHE TEMPERATURE OF THE CONTINUOUSLY CIRCULATING STREAM OF SLURRY FOR ASUBSTANTIAL PORTION OF ITS CIRCULATING CYXLE AT A TEMPERATURE FAVORAVLETO THE DESIRED REACTION AND DRAWING OFF FROM THE SYSTEM THE LIQUIDDITHLI-OPHOSPHATE ACID ESTER AT ABOUT ITS RATE OF FORMATION.